The present invention relates generally to a door opener and, more particularly, to an opener for a door on a gravity flow grain vehicle which provides a large mechanical advantage until the door begins to move and then decreases the mechanical advantage to allow faster opening and closing of the door.
Gravity flow grain vehicles are well known in the art for transporting grain and other materials in an agricultural environment. Gravity flow vehicles are typically four-wheeled vehicles with two sides, a front, and a back. Typically, gravity flow vehicles empty from the side or rear of the vehicle. In a side emptying vehicle, the bottom of tile gravity bed vehicle slopes from the front toward the middle and from the back toward the middle. The floor of the gravity bed vehicle also typically slopes from one side to the other. This arrangement allows feed to empty from a side of the gravity bed vehicle onto a grate or auger without the need for excessive shoveling or tipping of the gravity flow vehicle. Gravity flow vehicles typically have a gate or door mounted to the discharge side of the vehicle which slides up to allow the grain to discharge from the vehicle and slides down again to stem the flow of the grain from the vehicle. The door is usually moved upward and downward by means of a hand wheel secured by a cross bar to the sides of the gravity flow vehicle. The hand wheel turns an axle which is connected to a pinion which engages a rack secured to the door. As the hand wheel turns the pinion, the pinion forces tile rack along with the door upward or downward to open or close the door and thereby increase or decrease the flow of grain from the vehicle.
Although the standard gravity flow vehicle and door assembly is very useful in the agricultural environment, a major disadvantage of the standard door opening assembly is the great difficulty encountered in first opening the door when the gravity flow vehicle is full of grain. When the gravity flow vehicle is full of grain, the grain exerts a tremendous amount of force against the door which presses the door firmly against the rails along which the door slides upward and downward. The door thus becomes wedged against the rails making upward and downward movement very difficult. A great deal of force must often be applied to the hand wheel to move the door open even a small distance to allow grain to begin to flow. Once the grain begins to flow, however, the shifting of the vehicle's contents eases the pressure against the door thereby allowing the door to be more easily opened or closed. Although it would be possible to increase the size of the hand wheel or decrease the size of the pinion to increase the mechanical advantage needed to open the door, this increase in mechanical advantage would also decrease the speed at which the door may be opened or closed after the grain begins to flow. It would, therefore, be desirable to create a door opener which had a very large mechanical advantage as the door is opened a very small amount to allow the pressure of the grain against the door to be overcome, yet had a lower mechanical advantage once the door began to open to allow the door to be opened and closed quickly.
The difficulties in the prior art door openers are substantially eliminated by the present invention.